I want my clients to be able to pick colors for buttons,table borders, table headers

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If I had to put my hand to it I'd go about it this way:
First, create your style sheet for the entire site. Make sure to keep all elements grouped, so that you can globally apply style changes across the board. Then, access your css selectors and reapply color and font values.

At the end of the day, this really is just DHTML. Not much to it.
If you need some examples, let me know... I'm sure I can put something small together.

- Pip---------------------------------------------------------------------------------Nothing takes the taste out of peanut butter quite like unrequited love.